Node Memcached Append Operation (Detailed Guide w/ Code Examples)

Use Case(s)

The 'append' operation in Memcached is commonly used when you need to add some data at the end of existing data without overwriting it. This can be useful in scenarios where you're logging events or messages and want to add new entries at the end.

Code Examples

Here's an example using the memcached package in Node.js.

First, let's set a key-value pair:

const Memcached = require('memcached');
let memcached = new Memcached('localhost:11211');

memcached.set('key', 'Hello', 10000, function(err) {  
  // 10000 is the expiration time in seconds
  if(err) console.log(err);
});

Now, let's append " World" onto our existing value "Hello":

memcached.append('key', ' World', function(err){
  if(err) console.log(err);
});

After this operation, if we get the value of the 'key', it will be "Hello World".

Best Practices

• It's important to note that Memcached's append operation doesn't create a key if it doesn't exist, unlike set operation. So make sure the key exists before trying to append data to it.
• Keep in mind that Memcached is not a persistent storage and data stored can be evicted based on memory usage and the eviction policy.

Common Mistakes

• Trying to append to a non-existent key. As mentioned above, Memcached won't automatically create a key for you when you're using the append operation.
• Not handling errors properly. Make sure to handle any potential errors that may occur during the append operation.

FAQs

Q: Can we prepend data in Memcached?
Yes, just like append operation, Memcached also supports the 'prepend' operation which adds data to the beginning of an existing key's value.

Q: Is there a limit to how much data can be appended to a key?
As of the last update, each value in Memcached is limited to 1MB by default. The total can be increased or decreased by changing the item size max when starting the server.